The present invention relates to a method for launching counter-measures, such as flares and chaff, from a dispenser which is mounted on an aircraft. The invention also relates to an arrangement for storing and launching counter-measures, such as flares and chaff, comprising an elongate body with a plurality of compartments which are provided with openings and are separated in the longitudinal direction of the elongate body by partition walls and are used for storing the counter-measures, the arrangement being designed to be mounted on an aircraft of the aeroplane type, with the longitudinal direction of the elongate body essentially coinciding with the flight direction of the aircraft, and the counter-measures being connected to a firing control unit for feeding firing signals to the counter-measures. The counter-measures can consist of passive means, such as chaff foil or metal-coated glass fibres, but can also consist of flares, for example IR flares, or other active measures.
An example of a previously known arrangement or dispenser which is used for launching counter-measures and is provided with compartments is described in our own patent U.S. Pat. No. 4,679,483. In this case, the dispenser is configured and mounted on the aeroplane in such a way that the counter-measures are launched obliquely rearwards and downwards relative to the aeroplane.
Another example of a dispenser is known from U.S. Pat. No. 4,524,670. In this case, the dispenser is mounted on the underside of the aeroplane for launching the counter-measures downwards relative to the aeroplane.
The above two examples are examples of counter-measure dispensers which in historical terms have been able to function well, i.e. to successfully divert enemy attack, for example in the form of a target-seeking missile, towards the decoy target. However, over the course of time, target-seeking functions have been developed further, and there is now therefore a greater possibility of distinguishing the decoy target from the aeroplane. For example, the target seeker can be specifically programmed to handle the preliminary phase of activation of counter-measures. Information which can be used in this connection is the direction in which the counter-measures are launched relative to the aeroplane. In principle, the target seeker expects the counter-measures to be launched downwards, obliquely rearwards, or possibly rearwards.
A particular problem in launching flares is that the flares need time to develop into fully active decoy targets. There is a risk that the flares will only become fully active decoy targets at such a great distance from the aeroplane that a target seeker will be able to continue to follow the plane without any great problem.
One object of the present invention is to make available a method for launching counter-measures and an arrangement for storing and launching the counter-measures which increase the possibility, compared to known techniques, of avoiding threats, for example in the form of target-seeking missiles, enemy aircraft or the like.
Another object is to prevent the occurrence of vibration disturbances which are primarily caused by inherent oscillations in compartments which have been emptied of counter-measures.
The objects of the invention are achieved by means of a method which is characterized in that the counter-measures are launched in a direction obliquely forwards and upwards relative to the aircraft, and in that, in order to facilitate launching of the counter-measures, a low dynamic pressure is created permanently across the dispenser""s launch openings by means of fixed means acting on the air stream, and also by means of an arrangement characterized in that the arrangement is designed to be mounted on the top of the aircraft, and in that the compartments are provided with openings and are intended for launching the counter-measures in a direction obliquely forwards and upwards relative to the aircraft. By launching the counter-measures in the direction in accordance with our invention, a separating procedure unknown to today""s target seekers is obtained. Re-programming to the novel separation procedure is not a successful solution since it is then more difficult to identify previously known separation procedures. By launching the flares in the direction according to our invention, the flares have time to develop to fully active decoy targets before they pass the main heat source of the plane pertaining to the heat generation of the jet engines.
In this connection it may be noted that it is known per se to arrange a launching device on a plane which launches bombs or missiles obliquely forwards, see U.S. Pat. No. 3,517,584. The object of doing this is to effect launching which does not affect the plane""s speed and position despite the fact that very heavy objects are being launched. The solution is based on launching the bombs or missiles obliquely forwards by controlling guide rails. As soon as the bombs or the missiles leave the guide rails and thus the discharge opening, they lie in a rearwardly directed trajectory relative to the aeroplane and are only then activated. During the actual launch phase for a missile or a bomb, a hatch is opened which in the opened state has the task of reducing the air resistance in the slipstream. The slipstream is employed to quickly lift missiles or bombs away from the discharge opening. When closed, the hatches form an even, streamlined structure.
This launching of bombs or missiles in accordance with the above paragraph cannot be compared with the arrangement according to the invention for launching counter-measures, such as flares and chaff. Where counter-measures are concerned, it is lighter objects that are being launched and these objects are activated directly or shortly after they have left the discharge opening and in a first stage act near the aeroplane to create a favourable starting point for misleading radar, IR target seekers, or the like. On discharge, the air stream is disturbed such that the counter-measures can be kept near the aeroplane for as long as possible. The air stream is lifted over the discharge opening in order to minimize impact or relative wind against the counter-measures and to prevent transmission of vibrations to the aeroplane.
The counter-measures can advantageously be launched obliquely forwards and upwards and to the side. By adding in a lateral component, the launched counter-measures can be guided out further from the main body of the aeroplane. Such an arrangement reduces the risks of inadvertent collisions occurring between counter-measures and aeroplane body.
The compartments are suitably designed to slope forwards 30xc2x0 to 60xc2x0 and preferably about 45xc2x0 relative to the aircraft.
It should be emphasized here that it is not just the compartments which control the direction of launching. It also depends on how the counter-measures, preferably in cartridge form, are arranged in the compartments. The cartridges can to a certain extent be turned in the compartments. The inclination of the cartridges can be altered relative to the longitudinal and transverse walls of the compartments. In addition, the cartridges can be arranged to lie with the opening side essentially diagonal relative to the openings of the compartments. In principle, all geometrically possible positions can be considered for acting on the direction of launching and may be used.
To make it easier to launch the counter-measures obliquely forwards and upwards, the elongate body of the arrangement is provided with fixed means acting on the air stream in order to permanently create a low dynamic pressure across the compartment openings. This reduces the forces which act on the counter-measures during the phase when they leave the compartments of the elongate body via the compartment openings. The effect on the counter-measures during the launching phase is less, the result of which is that the launching force can be limited and the risks of damage to the counter-measures is reduced. For example, breaks on flares can be avoided.
When a compartment has been emptied of its contents of counter-measures, the compartment can act as a barrel which oscillates at its inherent frequency. Under unfavourable conditions, extremely high noise levels can occur. The creation of a low dynamic pressure across the compartment openings has been shown to effectively counteract oscillations caused by the inherent frequencies of the compartments, since the low dynamic pressure near the openings of the compartments means low energy.
Low dynamic pressure across the compartment openings can be created in a number of ways and, in particular, several measures can be combined to produce a low dynamic pressure across the whole row of compartment openings.
According to an advantageous embodiment, the means for creating a low dynamic pressure across the compartment openings comprise a finish towards the front compartment of the elongate body at an upwardly directed angle, preferably of the order of 15xc2x0, formed in the upper part of the front end of the elongate body.
According to another advantageous embodiment, the means for creating a low dynamic pressure across the compartment openings comprise partition walls with top parts shaped with an upwardly directed angle, preferably of the order of 15xc2x0. The partition walls are advantageously designed with a not inconsiderable thickness, preferably in the range of 10 to 30 mm, for example 15 mm.
According to a further advantageous embodiment, the means for creating a low dynamic pressure across the compartment openings comprise rounded edges designed in the transverse direction of the elongate body near the compartment openings.
According to yet another advantageous embodiment, the means for creating a low dynamic pressure across the compartment openings comprise spoiler elements arranged on the upper part of the front end of the elongate body.